Now you’re blithering.
You claim that the purpose of imprisonment is to protect society from the criminal, and that therefore killing the criminal is not acceptable.
You fail to address the fact that a dead ciminal will NEVER AGAIN offend agaisnt anyone.
Your argument fails the basic test of self consistency.
Perhaps you are content with that; I find it (your argument) ludicrous.
Who's blithering? A dead anyone will NEVER AGAIN offend anyone. Why not kill everyone, that way nobody offends anybody.
You've changed the issue. The issue and my argument is not "never again offend against anyone", but keeping society safe by the incarceration of dangerous criminals.